Signal transmitter linearization

• US 8,498,590 B1
• Filed: 03/30/2007
• Issued: 07/30/2013
• Est. Priority Date: 04/04/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Rashev, Peter Zahariev, Tholl, David M., Minderhoud, Kenneth
• Primary Examiner(s): Nguyen, Simon
• Application Number:
  US11/694,794
• Time in Patent Office: 2,314 Days
• Field of Search: 4551142-1151, 455/126, 4551271-1272, 455/425, 455/424, 455/456.5, 455/456.6, 455/561, 455/550, 455/1, 455/575.1, 455/501, 455/522, 455/63.1, 455/570, 455/114.3, 375295-297, 375/135, 375/146, 375/267, 330/291, 330/296, 330/129, 330/130, 330/131, 330/132, 330/149, 330/275, 330/285, 330/136, 330/289
• US Class Current: 455/114.2
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04B 2001/0433 with linearisation using feedback

Abstract

A linearizer for a non-linear transmitter and method include a gain regulator and predistorter adapted to be coupled to a non-linear transmitter in various configurations. Bounding controllers are coupled to the gain regulator and predistorter to maintain normal operation of a transmit path to prevent unstable transmitter operation.

Claims

1. A linearizer for a non-linear transmitter, the linearizer comprising:

a feedback receiver;

a gain regulator continuously adapted to be coupled to a non-linear transmitter;

an adaptive loop gain controller coupled to the gain regulator;

a loop gain bounding controller that receives feedback from a non-linear transmitter output and is coupled to control the gain regulator;

a continuously adaptive predistorter to apply complex-number amplification to provide a predistortion signal using continuously adapted predistortion values as a function of the feedback for the non-linear transmitter;

an adaptive predistorter controller to estimate the nonlinearity present in the adaptive loop and control the predistorter; and

a predistortion bounding controller coupled to receive signals from the non-linear transmitter and separately coupled to receive signals from the feedback receiver to prevent unstable transmitter operation by providing predistortion control signals to provide limits on the predistorter and providing adaption control signals to the adaptive predistorter controller to modify updating of the predistortion values, wherein at least one of the signals from the non-linear transmitter or the signals from the feedback receiver comprise a flag indicating saturation or overflow of an input to the non-linear transmitter or the feedback receiver, respectively.

2. The linearizer of claim 1 wherein the loop gain bounding controller limits a dynamic range of gain values for the gain regulator, the adaptive loop gain controller having a parametric output updating gain regulation values.

3. The linearizer of claim 1 wherein the predistortion bounding controller modifies the predistortion values as a function of present and past values in a moving average sense in order to reduce random variations.

4. The linearizer of claim 1 wherein the predistortion bounding controller modifies predistortion values as a function of present and past values in a moving average to reduce random variations.

5. The linearizer of claim 1 wherein the predistortion bounding controller limits an amount by which predistortion values are changed.

6. The linearizer of claim 1 wherein the predistortion bounding controller stops an adaptive process or resets predistortion values to an initial or recently estimated suitable state.

7. A linearizer for a non-linear transmitter, the linearizer comprising:

a feedback receiver;

a gain regulator continuously adapted to be coupled to a non-linear transmitter;

an adaptive loop gain controller coupled to the gain regulator;

a loop gain bounding controller that receives feedback from a non-linear transmitter output and is coupled to control the gain regulator;

a predistorter adapted to be coupled to the non-linear transmitter;

a continuously adaptive predistortion controller coupled to the predistorter using continuously adapted predistortion values as a function of the feedback; and

a predistortion bounding controller separately coupled to receive signals from each of the adaptive predistortion controller, the non-linear transmitter, and the feedback receiver to prevent unstable transmitter operation by providing predistortion control signals to provide limits on the predistorter and providing adaption control signals to the predistortion bounding controller to modify updating of the predistortion values, wherein at least one of the signals from the non-linear transmitter or the signals from the feedback receiver comprise a flag indicating saturation or overflow of an input to the non-linear transmitter or the feedback receiver, respectively.

8. The linearizer of claim 7 wherein the gain regulator is coupled to an output of the predistorter and directly coupleable to the non-linear transmitter.

9. The linearizer of claim 7 wherein the gain regulator is adapted to be coupled to the non-linear transmitter via the adaptive predistortion controller and predistorter.

10. The linearizer of claim 7 wherein the predistortion bounding controller limits a dynamic range of applied predistortion values and limits an amount by which predistortion values are changed via the predistortion controller.

11. The linearizer of claim 7 wherein the predistortion bounding controller modifies predistortion values as a function of present and past values in a moving average to reduce random variations.

12. The linearizer of claim 7 wherein the predistortion bounding controller limits an amount by which predistortion values are changed.

13. The linearizer of claim 7 wherein the predistortion bounding controller stops an adaptive process or resets predistortion values to an initial or recently estimated suitable state.

14. The linearizer of claim 7 wherein the loop gain bounding controller limits a dynamic range of gain values for the gain regulator.

15. The linearizer of claim 7 wherein the loop gain bounding controller limits a gain value update or change rate.

16. The linearizer of claim 7 wherein the loop gain bounding controller may stop gain regulation.

17. The linearizer of claim 7 wherein the loop gain bounding controller resets gain values to initial or recently estimated suitable values.

18. The linearizer of claim 7 and further comprising a non-linear transmitter and wherein the feedback receiver comprises a linear receiver that provides feedback to the gain regulator and adaptive predistortion controller.

19. The linearizer of claim 7 wherein the predistortion bounding controller is coupled to receive a power level of the input signal, a parametric control output of the adaptive predistortion controller, actual predistortion values used by the predistorter, indications of saturation or overflow of the predistorted signal in the transmitter, and indications of saturation or overflow of an output signal in a feedback receiver.

20. A method comprising:

obtaining feedback from signals transmitted by a non-linear transmitter;

predistorting an input signal for the non-linear transmitter using continuously adapted predistortion values as a function of the feedback;

bounding predistortion values used to predistort the input signal as a function of signals from the non-linear transmitter and as a function of signals from a linear receiver by providing predistortion control signals to control predistorting of the input signals and providing adaption control signals to modify updating of the predistorting of the input signals, wherein at least one of the signals from the non-linear transmitter or the signals from the linear receiver comprise a flag indicating saturation or overflow of an input to the non-linear transmitter or the linear receiver, respectively;

regulating gain applied to the input signal by use of continuously adapted gain regulation values and the feedback; and

bounding the gain regulation values to limit loop gain as a function of adaptive loop parametric output to prevent unstable transmitter operation.